The present invention relates to an aluminum alloy composite material for brazing, which is improved in strength, corrosion resistance and brazability, and which provides remarkable advantages when used for a tube member of a radiator assembled by the Nocolok brazing method.
Aluminum alloy composite materials for brazing are used for a tube member of a brazed radiator, etc., and conventionally, brazing sheets comprising Al-Mn alloy A3003 as a core member and an Al-Si filler member clad on the core member are used for this purpose.
The brazing sheet with the A3003 core member, however, has a post-brazing strength of not greater than 2 kgf/mm.sup.2 or thereabouts and is not sufficiently resistant to corrosion.
If Mg is added to the alloy of the core member, the strength of the composite material can be improved, but this modification results in an increased erosion of the core member due to the filler member and also in a reduction in brazability and corrosion resistance. In the case of the Nocolok brazing method, which is widely used, a Mg content in the core member in excess in 0.2% entails a substantial drop in brazability, and accordingly, addition of Mg to the core alloy must be restricted.
Thus, with conventional techniques, it is difficult to obtain an aluminum alloy composite material for brazing which has high strength and high corrosion resistance and yet is excellent in brazability. As for heat exchangers such as an automobile radiator, thin materials are needed to reduce the weight and cost, and accordingly, there is a demand for an aluminum alloy composite material which has high strength and high corrosion resistance and is excellent in brazability, but no such material has been developed yet.